1. Field of Invention
The present invention relates to an improved chlorosulfonic acid composition useful in making a high clarity sulfated salt of a C.sub.8-22 natural or synthetic predominantly straight chain aliphatic primary alcohol also referred to as shampoo base or detergent base and to a process for making the improved chlorosulfonic acid composition.
2. Related Art
The soap and detergent industry requires a high clarity base for some of its products so that the coloring agents they add are not adversely effected. The diluted, neutralized sulfated salt of a C.sub.8-22 natural or synthetic predominantly straight chain aliphatic primary alcohol used as a shampoo base, for example, must be almost "water white", otherwise its normal yellow color would cause a green product to result when blue coloring agents are added. Clarity can be measured by percent light transmittance (%LT). To be almost "water white", the material's percent light transmittance must be greater than 90% when measured at a 425 nanometer (nm) wave length in a 1 cm diameter cell. When the %LT is in the 70's or 80's, the material appears yellow. There are equivalent alternate means for measuring clarity known to those skilled in the art.
The shampoo base is made by first sulfating a C.sub.8-22 natural or synthetic predominantly straight chain aliphatic primary alcohol, preferably a C.sub.12-16 lauryl alcohol and most preferably a natural C.sub.12-16 lauryl alcohol. This sulfation, yielding an alkylsulfuric acid, can be done with chlorosulfonic acid. The alkylsulfuric acid is neutralized by methods known in the art. For example, neutralization can be with an alkali metal base or ammonium base, preferably a hydroxide and most preferably sodium hydroxide or ammonium hydroxide, or an alkanolamine, preferably triethanolamine or diethanolamine to form the sulfated salt of the starting alcohol also referred to as shampoo base or detergent base. The resulting salt is then diluted to meet the shampoo or detergent manufacturer's specification for active ingredient.
It is known that the reaction of chlorosulfonic acid and the alcohol is usually vigorous and exothermic so that localized overheating during admixture of the acid and alcohol are difficult to avoid. Such overheating results in undesirable side reactions and decomposition leading to low yields and discoloration.
U.S Pat. No. 2,187,244 to Mills teaches a continuous process of directly mixing the acid and alcohol without temperature constraint followed by promptly arresting the reaction by cooling or neutralization as soon as the desired reaction has progressed to the desired extent and before the undesirable side reactions have taken place to a substantial extent to produce a light-colored product.
U.S. Pat. No. 3,234,256 to Kaplan teaches an apparatus and a process for maximizing dispersion of the acid stream in the alcohol by injecting a thin stream of the acid into the alcohol through one orifice below the surface of the acid. Simultaneously, a high velocity inert gas stream from a second orifice adjacent to the first orifice impinges on the acid stream so as to atomize it within the liquid to yield an improved-color product. Temperature is controlled between 10 and 100.degree. C and most preferably at 35 to 65.degree. C.
U.S. Pat. No. 3,277,145 to Schull, et al. teaches an apparatus and a process for facilitating control of temperature by spraying the chlorosulfonic acid into a highly turbulent confined stream of inert gas mixed with the alcohol in liquid phase so as to yield a turbulent froth which is maintained until esterification is complete. Temperature is controlled between 5 and 100.degree. C and most preferably at 35 to 40.degree. C.
U.S. Pat. No. 3,133,946 to Maurer, et al. teaches a method of purifying the alkylsulfuric acid made by reacting chlorosulfonic acid and an n-alkanol in an organic, low boiling solvent at low temperatures. The n-alkanol has the formula ROH wherein R is an n-alkyl group having from 12 to 22 carbon atoms. The reaction solution is cooled to below about 0.degree. C to crystallize the alkylsulfuric acid which is rapidly separated to recover a substantially pure material which can, in turn, be reacted to form a salt for use as a shampoo base.
A common technique for improving the %LT of the shampoo base is to bleach the final product with bleaching agents such as hydrogen peroxide. This bleaching procedure is undesirable due to added cost and reduced productivity brought about by the added processing step. Also, certain sulfated salts such as amine lauryl sulfates cannot be successfully bleached to the desired %LT by this method without generating undesired side products which, for example, prevent use in cosmetic applications.
The chlorosulfonic acid (CSA) used to sulfate the alcohol is made by reacting anhydrous hydrogen chloride and sulfur trioxide. U.S. Pat. No. 2,377,642 to Mooney et al. teaches an improved process for manufacturing CSA. Mooney et al. teach that it is known to produce CSA by mixing sulfur trioxide-containing gases with hydrochloric acid-containing gases with cooling and that it is advantageous to keep the temperature at about 70.degree. C and certainly not above 100.degree. C to prevent the formation of pyrosulfuryl chloride (PSC). Mooney et al. teach a continuous reaction with the sulfur trioxide in excess, condensation of the CSA, and then contacting the condensed CSA with a hydrogen chloride-containing gas to convert any sulfur trioxide that dissolved in the CSA to CSA. The mixed reaction gases, after separation of the liquid CSA, are preferably treated to recover CSA remaining as a mist and then contacted with 95-98% sulfuric acid to recover sulfur trioxide values.
U.S. Pat. No. 2,311,619 to N. A. Laury teaches a process wherein the sulfur trioxide and hydrogen chloride are reacted in the presence of chlorosulfonic acid as a solvent at about 98.degree. C.
Japanese Patent Publication No. 7,024,648-R assigned to Mitsubishi Chemical Industry, Ltd., teaches a high temperature process for manufacturing CSA. Gaseous sulfur trioxide and gaseous hydrogen chloride react at a temperature of 151.3-153.degree. C to produce gaseous CSA which is then condensed. A portion of the condensed CSA is recycled to the reaction tower and a portion is diverted to a decomposition vessel where the by-product pyrosulfuryl chloride (PSC) is decomposed by adding 1.0-3.0% anhydrous sulfuric acid and 15-22 cubic meters per hour of anhydrous hydrogen chloride.